Film inspection device, film inspection method, and film production method

ABSTRACT

A defect of a film is accurately inspected. A film inspection device includes: a light-receiving device generating a signal by receiving light which returns via a film after having been applied to the film, the signal being for detecting a defect included in the film; and a reflecting roller carrying the film while supporting the film from a side opposite to the light-receiving device in a field of view of the light-receiving device.

This Nonprovisional application claims priority under 35 U.S.C. § 119 onPatent Application No. 2015-143382 filed in Japan on Jul. 17, 2015, theentire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates to a method of inspecting a defect of afilm being carried.

BACKGROUND ART

An optical technique is often used in inspection of a defect of a filmbeing carried. Patent Literature 1 discloses defect inspection in whichan object to be inspected, such as a film, is inspected for defect insuch a manner that visible light and invisible light from a light sourceare applied to the object and light reflected from the object isreceived. Patent Literature 2 discloses the use of defect inspection inwhich an image of light applied to both sides of a film is captured andthe image is processed. In a film defect inspection that uses reflectionof light in order to inspect a film for defect, a light source and alight-receiving device are arranged on a same side with respect to thefilm, and light which is emitted from the light source, applied to thefilm, and then reflected due to a defect such as the presence of aforeign matter is collected at the light-receiving device.

CITATION LIST Patent Literature

Patent Literature 1

Japanese Patent Application Publication, Tokukai, No. 2014-20910 A(Publication Date: Feb. 3, 2014)

Patent Literature 2

Japanese Patent Application Publication, Tokukai, No. 2008-116437 A(Publication Date: May 22, 2008)

SUMMARY OF INVENTION Technical Problem

A film being carried often ‘wobbles’, that is, becomes displaced in adirection perpendicular to a surface of the film. The displacement canbe suppressed to some extent by creating tension in the film in alongitudinal direction of the film. However, as the tension increases,it becomes more likely that the film being carried stretches or breaks.It is therefore necessary to keep the tension under a certain degree.Further, in a case where the film wobbles, a change unrelated to adefect of the film is caused in intensity of reflected light that iscollected at the light-receiving device. The change prevents obtainingan accurate inspection result. This tendency is particularly prominentin a case where the film is a porous separator for a secondary cell orthe like, the separator having a low mechanical strength. The problemabove is not taken into consideration in the conventional techniquesdescribed in Patent Literatures 1 and 2. The present invention isaccomplished in view of the problem above. An object of the presentinvention is accurate measurement of a defect of a film being carried.

Solution to Problem

In order to attain the object, a film inspection device according to thepresent invention is a film inspection device including: alight-receiving device generating a signal by receiving light whichreturns via a film after having been applied to the film, the signalbeing for detecting a defect included in the film; and a first rollercarrying the film while supporting the film from a side opposite to thelight-receiving device in a field of view of the light-receiving device.

A film inspection method according to the present invention is a filminspection method including the steps of: (a) generating a signal byreceiving light which returns via a film after having been applied tothe film, the signal being for detecting a defect included in the film;and (b) carrying the film while supporting the film from a side oppositeto the light-receiving device in a field of view of the light-receivingdevice.

A film production method according to the present invention is a filmproduction method including: each step included in the film inspectionmethod above; and the step of (c) removing a defective portion of thefilm inspected on the basis of the signal generated in the step (a).

Advantageous Effects of Invention

According to the present invention, it is possible to inspect a defectof a film more accurately as compared with a conventional technique.Further, the present invention makes it possible to produce a filmhaving fewer defects as compared with a conventional technique.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows a lateral view and a cross-sectional view illustrating anarrangement of a film inspection device according to Embodiment 1.

FIG. 2 is a graph of an electrical signal outputted by a light-receivingdevice of the film inspection device illustrated in FIG. 1.

FIG. 3 is a lateral view illustrating possible positional arrangementsand possible postures of the light-receiving device and a reflectingroller of the film inspection device illustrated in FIG. 1.

FIG. 4 is a lateral view illustrating an arrangement of a filminspection device according to Embodiment 2.

FIG. 5 is a cross-sectional view illustrating an arrangement of a filminspection device according to Embodiment 3.

FIG. 6 is a lateral view illustrating a modified example of the filminspection device illustrated in FIG. 1.

FIG. 7 is a cross-sectional view illustrating another modified exampleof the film inspection device illustrated in FIG. 1.

DESCRIPTION OF EMBODIMENTS Embodiment 1 Arrangement of Film InspectionDevice 1

FIG. 1 is a view illustrating an arrangement of a film inspection device1 according to the present embodiment. (a) of FIG. 1 is a lateral viewand (b) of FIG. 1 is a cross-sectional view of a plane that includes alight-receiving device 12 and a reflecting roller 13 (first roller)which are illustrated in (a). Note that an XYZ-axis in FIG. 1corresponds to an XYZ-axis in each of other drawings.

The film inspection device 1 is a device which inspects a defect of afilm 2 being carried in a Y-axis positive direction. As illustrated in(a) and (b) of FIG. 1, the film inspection device 1 includes lightsources 11 a and 11 b, the light-receiving device 12, the reflectingroller 13, an inspection section 14, carrying rollers 3 a and 3 b(second roller). Note that for the sake of simplicity, the light sources11 a and 11 b are indicated with a broken line and the carrying rollers3 a and 3 b are omitted in (b) of FIG. 1.

(Film 2)

The film 2 is an imperforate film which has not been processed into aseparator for a secondary cell. Note that a separator for a secondarycell is a porous film which separates a positive electrode and anegative electrode of, for example, a lithium ion secondary cell fromeach other while allowing lithium ions between the positive electrodeand the negative electrode to be movable.

Specifically, the film 2 is a film obtained by molding a polyethyleneresin composition that is obtained by kneading ultrahigh molecularweight polyethylene and (i) inorganic filler (filler: for example,calcium carbonate or silica) or (ii) plasticizer (for example, lowmolecular weight polyolefin or liquid paraffin). The polyethylene resincomposition is obtained by, for example, kneading 100 parts by weight ofultrahigh molecular weight polyethylene, 100 parts by weight to 400parts by weight of an inorganic filler, and 5 parts by weight to 200parts by weight of low molecular weight polyolefin that has aweight-average molecular weight of 10,000 or less.

Note that an object inspected by the film inspection device 1 is notlimited to the film 2 described above, and can be any of items listedbelow. The object to be inspected preferably transmits light to someextent. In this case, it is possible to attain an advantageous effect,described later in the section “Influence of Color and Surface Roughnessof Outer Circumferential Surface of Reflecting Roller 13,” by thereflecting roller 13 (i.e., in an electrical signal corresponding toinspection light, a contrast between a normal portion and a defectiveportion of the film 2 can be enhanced or a noise component can bereduced). Note, however, that the object to be inspected can be a filmthat does not transmit light at all, such as a metal film having acertain degree of thickness. Also in this case, it is possible toachieve suppression of changes in position and posture of the film 2 inan inspection region with respect to the light-receiving device 12.

A film obtained by removing the inorganic filler or the plasticizer fromthe above-described film that is obtained by molding the polyethyleneresin composition

A stretched film obtained by uni-axially or bi-axially stretching theabove film

A film obtained by coating a stretched film with a solution containingaramid, and a laminated film on one side or both sides of which anaramid heat resistant layer is formed by removing a solvent from thesolution

A film obtained by coating a stretched film with a solution containingalumina/carboxymethylcellulose, and a laminated film on one side or bothsides of which an alumina heat resistant layer is formed by removing asolvent from the solution

A film obtained by coating a stretched film with a solution containingpolyvinylidene-fluoride, a laminated film on one side or both sides ofwhich an adhesion layer is formed by removing a solvent from thesolution

An optical film

Cloth, paper, pulp, or cellulose

The stretched films and the laminated films above are used as aseparator for a secondary cell. In recent years, demand for reducing athickness of a separator for a secondary cell is increasing, assecondary cells have an increasingly higher capacity. Specifically, aseparator having a film thickness of 5 μm to 10 μm for a secondary cellis in demand. Such a film has a particularly low strength and thereforehas a particularly high possibility of wobbling, stretching, orbreaking. The present invention therefore has a great advantageouseffect, which will be described later, on inspection of theabove-described separator for a secondary cell.

(Defect of Film 2)

A defect for which the film 2 is inspected by the film inspection device1 is, for example, the following foreign matter mixed in the film 2.

Metal (iron, stainless steel, aluminum, copper, zinc, brass, etc.)

Gel (ultrahigh molecular weight polyethylene etc.)

Aggregate of filler (calcium carbonate etc.)

Oil droplet

Roller abrasive

Metal oxide (aluminum oxide, chrome oxide, etc.)

Anti-seizure agent (metallic salt)

A foreign matter for which the film 2 is inspected by the filminspection device 1 thus has an optical property different from that ofthe film 2. Note that a hole, a crease, unevenness, and the like in thefilm 2 are also encompassed in the examples of a defect for which thefilm 2 is inspected by the film inspection device 1.

(Carrying Rollers 3 a and 3 b)

The carrying rollers 3 a and 3 b are rollers which carry the film 2 inthe Y-axis direction by rolling while in contact with the film 2. Asillustrated in (a) of FIG. 1, the carrying rollers 3 a and 3 b arecylindrical and rotatably supported. In a case where an externalcarrying device carries the film 2, the film inspection device 1 doesnot have to include the carrying rollers 3 a and 3 b. Note that thecarrying roller 3 a can be a reel-off roller for reeling off the film 2which is wound around a cylindrical core fitted in the carrying roller 3a. The carrying roller 3 b can be a reel-in roller for reeling the film2 in around a cylindrical core fitted in the carrying roller 3 b.

(Light Sources 11 a and 11 b)

The light sources 11 a and 11 b applies light to the film 2. Lightapplied by the light source 11 a is visible light. Light applied by thelight source 11 b is ultraviolet light or infrared light.

As illustrated in (b) of FIG. 1, the light sources 11 a and 11 b applieslight to almost an entire region of the film 2 in an X-axis direction.Note that the X-axis direction is a direction perpendicular to alongitudinal direction and a thickness direction of the film 2. Thelight sources 11 a and 11 b apply light to a same part of the film 2. Inorder to apply light in this manner, each of the light sources 11 a and11 b includes, for example, (i) a plurality of light emitting diodes(LEDs) arranged in the X-axis direction, (ii) other light emittingdevice(s), or (iii) a combination of an LED or another light emittingdevice, and a diffuser or a wavelength filter.

Note that in a case where light applied from outside of the filminspection device 1 to the film 2 can be used as the light applied tothe film 2, the film inspection device 1 does not have to include thelight sources 11 a and 11 b.

(Light-Receiving Device 12)

The light-receiving device 12 is a device which generates a signal fordetecting a defect included in the film 2 by receiving light thatreturns in a Z-axis positive direction via the film 2 after beingapplied to the film 2 by the light sources 11 a and 11 b.

Note that examples of the light that returns from the film 2 encompasses(i) light reflected from a surface or an inside of the film 2, (ii)light scattered from the surface or the inside of the film 2, and (iii)light which is transmitted through the film 2 and then reflected orscattered by the reflecting roller 13 so as to be transmitted throughthe film again. These examples of light are hereinafter correlativelyreferred to as ‘inspection light’.

The light-receiving device 12 includes a lens 15 which collectsinspection light. As illustrated in (b) of FIG. 1, the light-receivingdevice 12 collects inspection light from almost an entire region of thefilm 2 in the X-axis direction. The lens 15 has a depth of field whichis set so as to include almost an entire region of a front surface and aback surface of the film 2 on the reflecting roller 13.

The light-receiving device 12 further includes two charge coupleddevices (CCDs) 16 a and 16 b and two optical filters 17 a and 17 bcorresponding the respective CCDs. Each of the two CCDs 16 a and 16 bconverts collected inspection light into an electrical signal. The twooptical filters 17 a and 17 b are provided for the respective two CCDs16 a and 16 b, and only transmit respective specific light so that oneof the two CCDs 16 a can convert an optical component from the lightsource 11 a into an electrical signal and the other one of the two CCDs16 b can convert an optical component from the light source 11 b into anelectrical signal. This allows the light-receiving device 12 to dividecollected inspection light into an optical component from the lightsource 11 a and an optical component from the light source 11 b andconvert each optical component into an electrical signal.

(Reflecting Roller 13)

As illustrated in (a) and (b) of FIG. 1, the reflecting roller 13 isprovided in a position facing the light-receiving device 12 via the film2. The reflecting roller 13 supports the film 2 while in contact withone surface of the film 2 which surface is on a Z-axis negativedirection side, and rolls in a direction in which the film 2 is carried.

Accordingly, inspection light received by the light-receiving device 12is inspection light that is received via a part of the film 2 which partis supported by the reflecting roller 13 on the one surface, that is,via a part at which changes in position and posture of the film 2 withrespect to the light-receiving device 12 are suppressed.

Note that the carrying rollers 3 a and 3 b which carry the film 2 areprovided on a same side as the reflecting roller 13 with respect to thefilm 2, and in a position immediately before the reflecting roller 13and a position immediately after the reflecting roller 13, respectively,along a carrying path of the film 2.

The reflecting roller 13 reflects or scatters light that is transmittedthrough the film 2 among light applied by the light sources 11 a and 11b to the film 2. An outer circumferential surface, which comes incontact with the film 2, of the reflecting roller 13 is constituted byunmatted white- to ivory-colored vinyl chloride.

In the present application, ‘unmatted’ means that a glossiness (surfacestate) of the outer circumferential surface, which comes in contact withthe film 2, of the reflecting roller 13 as measured by use of, forexample, GlossChecker IG-331 (manufactured by HORIBA) is not less than10 but less than 76 relative to a glossiness of 100 which corresponds toa reflectivity of 10%, according to specular gloss at 60° which is atype of specular gloss measuring method under Japanese IndustrialStandard JIS-Z8741.

On the other hand, ‘matted’ means that the glossiness above is not lessthan 0 but less than 10. In a case where the glossiness is not less than76, the outer circumferential surface is defined to be a specularsurface. For example, the outer circumferential surface which isconstituted by vinyl chloride has a glossiness of not less than 60 butnot more than 70.

Note that a color of the outer circumferential surface of the reflectingroller 13 in the present embodiment does not need to be white of what iscalled an achromatic color, as long as the color allows the outercircumferential surface to reflect or scatter light sufficiently.Specifically, it is preferable that the outer circumferential surfacehas a lightness of not less than 7.0 but not more than 9.5 and a chromaof not less than 0.5 but not more than 3 according to the Munsell colorsystem, although a hue of the outer circumferential surface is notparticularly limited. For example, the outer circumferential surface inEmbodiment 1 has a hue of 5Y, a lightness of 9, and a chroma of 0.5. InEmbodiment 2 which is described later, the outer circumferential surfacehas a hue of 2.5Y, a lightness of 7.5, and a chroma of 2.

(Inspection Section 14)

As illustrated in (a) and (b) of FIG. 1, the inspection section 14 isconnected to the light-receiving device 12 and receives an electronicsignal converted by the light-receiving device 12. The electrical signalreflects intensity of inspection light that is received by thelight-receiving device 12 from almost an entire region of the film 2 inthe X-axis direction. On the basis of the electrical signal, theinspection section 14 inspects whether a defect of the film 2. Note thatthe film inspection device 1 can be connected to an external inspectionsection that has a function equivalent to that of the inspection section14. In this case, film inspection device 1 does not have to include theinspection section 14.

The inspection section 14 may be realized by a logic circuit (hardware)provided in an integrated circuit (IC chip) or the like or may berealized by software as executed by a CPU (Central Processing Unit).

In the latter case, the inspection section 14 includes: a CPU thatexecutes instructions of a program that is software realizing theforegoing functions; ROM (Read Only Memory) or a storage device (eachreferred to as “storage medium”) storing the program and various kindsof data in such a form that they are readable by a computer (or a CPU);and RAM (Random Access Memory) that develops the program in executableform. The object of the present invention can be achieved by a computer(or a CPU) reading and executing the program stored in the storagemedium. The storage medium may be “a non-transitory tangible medium”such as a tape, a disk, a card, a semiconductor memory, and aprogrammable logic circuit. Further, the program may be supplied to ormade available to the computer via any transmission medium (such as acommunication network and a broadcast wave) which enables transmissionof the program. Note that the present invention can also be implementedby the program in the form of a computer data signal embedded in acarrier wave which is embodied by electronic transmission.

<<Operation of Film Inspection Device 1>>

(Inspection of Presence or Absence of Defect)

An intensity of an electrical signal received by the inspection section14 from the light-receiving device 12 corresponds to an intensity ofinspection light from the film 2. In a case where the film 2 has adefect, the intensity of the inspection light changes. As such, theinspection section 14 can inspect whether or not a film 2 to beinspected for a defect has a defect by (i) holding, as a referencevalue, an electrical signal corresponding to an intensity of inspectionlight from another film 2 that is defect-less and obtained in advanceand (ii) comparing the reference value with an electrical signal to beinspected which corresponds to an intensity of inspection light from thefilm 2 to be inspected. For example, the inspection section 14 caninspect the presence or absence of a defect by deciding that ‘a defectis present’ in a case where a value obtained by dividing the electricalsignal to be inspected by the reference value is smaller than a certainvalue.

Note that the inspection section 14 can be configured such that theinspection section 14 receives from the light-receiving device 12 aplurality of electrical signals over multiple times, and using anaverage of the plurality of electrical signals as the reference value orthe electrical signal to be inspected. Note here that an electricalsignal undergoes variations according to a surface condition of a film 2even in a case where the film 2 has no defect. By averaging a pluralityof electrical signals, the inspection section 14 can obtain anelectrical signal in which the variations are suppressed.

(Inspection of Position of Defect)

FIG. 2 shows graphs of an electrical signal outputted from thelight-receiving device 12 of the film inspection device 1 of illustratedin FIG. 1. (a) through (d) of FIG. 2 are graphs corresponding to casesin which respective reflecting rollers 13 differing in surface color orprocessing method are used. A horizontal axis ‘inspection width’ of eachof the graphs corresponds to a position of the film 2 in the X-axisdirection. A vertical axis ‘signal intensity’ of each graph correspondsto an intensity of inspection light received by the light-receivingdevice 12 after having been reflected at the position, corresponding tothe horizontal axis, of the film 2 in the X-axis direction. A value ofan origin of the vertical axis is a lower limit value of an electricalsignal that can be outputted from the light-receiving device 12.

As illustrated in (a) of FIG. 2, an intensity of inspection light from acentral part of the film 2 in the X-axis direction is smaller than anintensity of inspection light from an end part of the film 2 in theX-axis direction. Accordingly, in a case where the inspection section 14receives the electrical signal shown in the graph of (a) of FIG. 2, theinspection section 14 can make an inspection as to a position of adefect such that “a defect that reduces an amount of inspection light ispresent in the central part of the film 2 in the X-axis direction”.

(Inspection of Size of Defect)

As a defect of the film 2 increases in size in the X-axis direction, arange in which the intensity of the electrical signal shown in (a) ofFIG. 2 decreases extends. Accordingly, on the basis of a waveform of theelectrical signal shown in the graph of (a) of FIG. 2, the inspectionsection 14 can inspect the size of the defect in the X-axis direction.Specifically, the inspection section 14 can inspect a size of a defectof the film 2 in the X-axis direction by (i) finding a range of theinspection width in which range an intensity of an electrical signal issmaller than a certain value and (ii) multiplying the range by amagnification of the lens of the light-receiving device 12 to therebyconvert the range into a length of the defect of the film 2 in theX-axis direction.

As a defect of the film 2 increases in size in the Y-axis direction, atime period in which an intensity of an electrical signal shown in thegraph of (a) of FIG. 2 decreases extends. Accordingly, the inspectionsection 14 can inspect a size of a defect in the Y-axis direction on thebasis of waveforms, received in succession, of an electrical signalshown in the graph of (a) of FIG. 2. Specifically, the inspectionsection 14 can inspect a size of a defect of the film 2 in the Y-axisdirection by (i) finding a time period in which an intensity of anelectrical signal is smaller than a certain value and (ii) multiplyingthe time period by a carrying speed of the film 2 to thereby convert thetime period into a length of the defect of the film 2 in the Y-axisdirection.

As described above, the inspection section 14 can inspect a size of thefilm 2 in X-axis and Y-axis directions.

(Inspection of Type of Defect)

In a case where a type of a defect of the film 2 varies, a degree of adifference between (i) a degree of change, caused between a case wherethe defect is present and a case where the defect is absent, inintensity (hereinafter referred to as ‘first intensity’) of inspectionlight corresponding to visible light from the light source 11 a and (ii)a degree of change, caused between a case where the defect is presentand a case where the defect is absent, in intensity (hereinafterreferred to as ‘second intensity’) of inspection light corresponding toinfrared light or ultraviolet light from the light source 11 b varies.In a case where a defect of the film 2 is, for example, metal, the firstintensity and the second intensity change to a similar extent. In a casewhere a defect of the film 2 is, for example, oil, the second intensitychanges by a greater ratio than a ratio by which the first intensitychanges. Therefore, it is possible to specify a type of a defect of thefilm 2 by (i) simultaneously measuring, by use of the light-receivingdevice 12, the first intensity of the visible light applied by the lightsource 11 a and the second intensity of the infrared light or theultraviolet light applied by the light source 11 b and (ii) comparingthe first intensity with the second intensity by use of the inspectionsection 14.

Note that in a case where of not performing the above-describedinspection of a type of a defect, the film inspection device 1 can beconfigured to include a single light source instead of two lightsources.

<<Advantageous Effect of Film Inspection Device 1>>

Since the film inspection device 1 includes the reflecting roller 13 asshown in (a) and (b) of FIG. 1, changes in position and posture of thefilm 2 with respect to the light-receiving device 12 can be suppressedin the inspection region in the film inspection device 1. Accordingly,the light-receiving device 12 of the film inspection device 1 can outputan electrical signal to which a defect of the film 2 is reflected moreaccurately, compared to a conventional film inspection device that doesnot include the reflecting roller 13.

Therefore, the film inspection device 1 has an advantageous effect ofbeing able to inspect a defect of the film 2 more accurately as comparedwith a conventional technique. Note that this advantageous effect isachieved not only in a case where the light-receiving device 12 and thereflecting roller 13 are arranged as illustrated in FIG. 1.

(Relation Between Field of View of Light-Receiving Device 12 andPositional Arrangement of Reflecting Roller 13)

FIG. 3 is a lateral view illustrating possible positional arrangementsand possible postures of the light-receiving device 12 and thereflecting roller 13 of the film inspection device 1 illustrated in (a)of FIG. 1. Note that for the sake of simplicity, the light sources 11 aand 11 b, the inspection section 14, and the carrying rollers 3 a and 3b are omitted in FIG. 3.

As shown by broken lines in FIG. 3, the light-receiving device 12collects inspection light from a field of view V which is an area fromwhich the lens of the light-receiving device 12 can collect inspectionlight to the CCDs. At a central part of the field of view V in theY-axis direction, the film 2 is carried while being supported by thereflecting roller 13 from a side opposite to the light-receiving device12.

Note that a relation between the field of view V of the light-receivingdevice 12 and a positional arrangement of the reflecting roller 13 isnot limited to the above, as long as the film 2 is carried while beingsupported from the side opposite to the light-receiving device 12 in thefield of view of the light-receiving device 12.

For example, the light-receiving device 12 can be moved to a position 12a. In this case, the field of view V is changed to a field of view Va,and the film 2 in the field of view Va is carried while being supportedby the reflecting roller 13 from the side opposite to thelight-receiving device 12 at an end part of the field of view Va in theY-axis direction. Note that the position 12 a illustrated in FIG. 3 is aposition shifted in a Y-axis negative direction with respect to thelight-receiving device 12, but the position 12 a can also be a positionshifted in a Y-axis positive direction with respect to thelight-receiving device 12.

Further, it is also possible to move the light-receiving device 12 to aposition 12 b and tilt the posture of the light-receiving device 12.Also in this case, the field of view V is changed to the field of viewVa and as described above, the film 2 in the field of view Va is carriedwhile being supported by the reflecting roller 13 from the side oppositeto the light-receiving device 12 at the end part of the field of view Vain the Y-axis direction. Note that the position 12 b illustrated in FIG.3 is a position shifted in the Y-axis positive direction with respect tothe light-receiving device 12, but the position 12 b can also be aposition shifted in the Y-axis negative direction with respect to thelight-receiving device 12.

In the cases above, inspection light received by the light-receivingdevice 12 includes inspection light which returns via a part P of thefilm 2 which part is supported by the reflecting roller 13, that is, viaa part P at which changes in position and posture of the film 2 withrespect to the light-receiving device 12 are suppressed. Consequently, achange unrelated to a defect of the film 2 is less likely to occur inlight intensity of inspection light received by the light-receivingdevice 12, as compared with an arrangement in which the reflectingroller 13 is not provided. As such, according to the film inspectiondevice 1, the light-receiving device 12 can output a signal whichreflects a defect of the film 2 more accurately as compared with aconventional film inspection device that does not include the reflectingroller 13.

Therefore, the film inspection device 1 has an advantageous effect ofbeing able to inspect a defect of the film 2 more accurately as comparedwith a conventional technique.

(Relation Between Optical Axis of Light-Receiving Device 12 andPositional Arrangement of Reflecting Roller 13)

The light-receiving device 12 collects inspection light by using, as acentral axis, an optical axis OA which is a straight line connectingbetween a center of the lens of the light-receiving device 12 and afocal point of the lens, as indicated by a chain line in FIG. 3. Theoptical axis OA passes through the part P, supported by the reflectingroller 13, of the film 2.

The optical axis OA is in such a positional relation with a rotationalaxis of the reflecting roller 13 that the optical axis OAperpendicularly intersects with the rotational axis. It is also possibleto move the light-receiving device 12 to a position 12 c and tilt theposture of the light-receiving device 12, so that the optical axis OAchanges to an optical axis OAa. Note that although the position 12 cillustrated in FIG. 3 is a position that is shifted in the Y-axispositive direction with respect to the light-receiving device 12 andtilted in a clockwise direction about the X-axis as a central axis, theposition 12 c can also be a position that is shifted in the Y-axisnegative direction and tilted in a counterclockwise direction about theX-axis as a central axis.

In the cases above, inspection light received by the light-receivingdevice 12 includes an increased proportion of inspection light thatreturns via the part P, at which changes in position and posture of thefilm 2 are suppressed, of the film 2. Accordingly, a change in lightintensity that is unrelated to a defect of the film 2 is even lesslikely to occur.

Note that in a case where the optical axis OA is in such a positionalrelation with the reflecting roller 13 that the optical axis OA passesthrough a position of contact between the film 2 and the reflectingroller 13 and perpendicularly intersects with the rotational axis of thereflecting roller 13, that is, in a case where the reflecting roller 13is in a position facing the light-receiving device 12 via the film 2,inspection light received by the light-receiving device 12 includes anincreased proportion of inspection of light that returns via the part Pof the film 2. Accordingly, a change unrelated to a defect of the film 2is still even less likely to occur in light intensity.

(Influence of Color and Surface Roughness of Outer CircumferentialSurface of Reflecting Roller 13)

Suppression of changes in position and posture of the film 2 withrespect to the light-receiving device 12 in the inspection region isachieved even in a case where inspection light does not include lightwhich is transmitted through the film 2 and then reflected or scatteredby the reflecting roller 13 so as to be transmitted through the film 2again.

On the other hand, in a case where inspection light includes light whichis transmitted through the film 2 and then reflected or scattered by thereflecting roller 13 so as to be transmitted through the film 2 again,the following things become possible by adjusting properties (color,surface roughness, etc.) of an outer circumferential surface, whichcomes in contact with the film 2, of the reflecting roller 13. That is,as shown in the graph of (a) of FIG. 2, (i) a contrast between a partcorresponding to a normal part of the film 2 and a part corresponding toa defective part of the film 2 is enhanced in an electrical signalcorresponding to inspection light and (ii) a noise component can bereduced in the electrical signal corresponding to the inspection light.The following description will discuss an influence of properties of anouter circumferential surface, which comes in contact with the film 2,of the reflecting roller 13.

As described above, the electrical signal shown in the graph of (a) ofFIG. 2 is an electrical signal outputted from the light-receiving device12 in a case of employing an arrangement in which a reflecting roller 13whose outer circumferential surface coming in contact with the film 2 iswhite and not matted (has a low surface roughness) is used. A foreignmatter contained in the film 2 often has a dark color. With thearrangement above, a contrast between the foreign matter and the film 2is enhanced on the reflecting roller 13, so that the film inspectiondevice can inspect a defect of the film more accurately.

An electrical signal shown in the graph of (b) of FIG. 2 is anelectrical signal outputted from the light-receiving device 12 in a caseof using a reflecting roller 13 whose outer circumferential surfacecoming in contact with the film 2 is white and matted. As shown in thegraph of (b) of FIG. 2, the electrical signal has a waveform which, in acentral part of the inspection width, resembles the waveform of theelectrical signal shown in the graph of (a) of FIG. 2, but in an endpart of the inspection width, changes to a relatively great extent dueto a noise component. In this case, the inspection section 14 may not beable to detect a significant difference by comparing the reference valueand the electrical signal to be inspected which are described above.Therefore, in inspection of a defect of the film 2, it tends to bepreferable that the outer circumferential surface, which comes incontact with the film 2, of the reflecting roller 13 be not matted.

An electrical signal shown in the graph of (c) of FIG. 2 is anelectrical signal outputted from the light-receiving device 12 in a caseof using a reflecting roller 13 whose outer circumferential surfacecoming in contact with the film 2 is gray and not matted. As shown inthe graph of (c) of FIG. 2, the electrical signal has a waveform inwhich the ‘signal intensity’ reaches a lower limit value in a centralpart of the inspection width. Further, values of the ‘signal intensity’are generally lower than those of the ‘signal intensity’ of theelectrical signal shown in the graph of (a) of FIG. 1. In this case, theinspection section 14 may not be able to detect a significant differenceby comparing the reference value and the electrical signal to beinspected which are described above. Therefore, in inspection of adefect of the film 2, it tends to be preferable that the outercircumferential surface, which comes in contact with the film 2, of thereflecting roller 13 be white.

An electrical signal shown in the graph of (d) of FIG. 2 is anelectrical signal outputted from the light-receiving device 12 in a caseof using a reflecting roller 13 whose outer circumferential surfacecoming in contact with the film 2 is gray and matted. As shown in thegraph of (d) of FIG. 2, the electrical signal has a waveform which, in acentral part of the inspection width, resembles the waveform of theelectrical signal shown in the graph of (c) of FIG. 2, but in an endpart of the inspection width, changes to a relatively great extent. Inthis case, the inspection section 14 may not be able to detect asignificant difference by comparing the reference value and theelectrical signal to be inspected which are described above. Therefore,in inspection of a defect of the film 2, it tends to be preferable thatthe outer circumferential surface, which comes in contact with the film2, of the reflecting roller 13 be white and not matted.

(Film Inspection Method)

The present invention also includes a film inspection method carried outby the film inspection device 1. The film inspection method includes astep (a) of generating a signal by receiving, with use of thelight-receiving device 12, inspection light which returns via the film 2after having been applied to the film 2, the signal being for detectinga defect included in the film 2 and a step (b) of carrying the film 2while supporting the film 2 from a side opposite to the light-receivingdevice 12 in the field of view V or the field of view Va of thelight-receiving device 12.

The step (a) is a step in which the light-receiving device 12 generatesthe electrical signal shown in the graph of (a) of FIG. 2 by receivinglight applied by the light sources 11 a and 11 b to the film 2 asillustrated in (a) and (b) of FIG. 1. The step (b) is a step in which asillustrated in (a) of FIG. 1, the film 2 is carried in the Y-axispositive direction along a path defined by the carrying rollers 3 a and3 b.

The film inspection method described above makes it possible to inspecta defect of the film 2 more accurately as compared with a conventionaltechnique.

(Film Production Method)

The present invention also encompasses a film production method in whichthe film inspection method described above is used. The film productionmethod includes a step (c) of removing a defective portion of the filmon the basis of a result of receiving light in the step of receivinglight, as well as the steps (a) and (b) included in the film inspectionmethod described above.

The step (c) is a step which is carried out on a Y-axis positivedirection side of the film inspection device 1 illustrated in (a) and(b) of FIG. 1. In the step (c), a defective portion of the film 2inspected on the basis of the result of receiving light in thelight-reception step is removed by being cut off. The film from whichthe defective portion is cut off is, for example, connected with anotherfilm.

The film production method described above enables production of a film2 having less defects as compared with a film produced by a conventionaltechnique.

Embodiment 2

In the present embodiment, the same reference signs will be given tomembers each having the same function as a member described in theembodiment above, and descriptions on such a member will be omitted. Thesame applies to other embodiments described below.

<<Arrangement of Film Inspection Device 1A>>

FIG. 4 is a lateral view illustrating an arrangement of a filminspection device 1A according to the present embodiment. As illustratedin FIG. 4, the film inspection device 1A includes the same members asthose included in the film inspection device 1. However, unlike the filminspection device 1, the film inspection device 1A is arranged such thatthe carrying rollers 3 a and 3 b are in contact with the film 2 on aZ-axis positive direction side. Note that the Z-axis positive directionside is a side opposite to the reflecting roller 13 with respect to thefilm 2.

<<Operation and Advantageous Effect of Film Inspection Device 1A>>

The film inspection device 1A operates in the same manner as the filminspection device 1, and can inspect a defect of the film 2 moreaccurately than a conventional technique. Further, in the filminspection device 1A, the carrying rollers 3 a and 3 b work so as topress the film 2 against the reflecting roller 13. This allows furthersuppression of changes in position and posture of the film 2 withrespect to the light-receiving device 12. Accordingly, the filminspection device 1A can inspect a defect of the film 2 more accurately.

Note, however, that in the film inspection device 1, the carryingrollers 3 a and 3 b and the reflecting roller 13 are provided on thesame side with respect to the film 2. This allows the film inspectiondevice 1 to secure more space for the light sources 11 a and 11 b andthe light-receiving device 12 as compared with the film inspectiondevice 1A. Accordingly, there is more flexibility in providing the lightsources 11 a and 11 b and the light-receiving device 12 in the filminspection device 1.

Note that the present invention encompasses both (i) the above-describedfilm inspection method carried out with use of the film inspectiondevice 1A and (ii) the above-described film production method carriedout with use of the film inspection method.

Embodiment 3 Arrangement of Film Inspection Device 1B

FIG. 5 is a cross-sectional view illustrating an arrangement of a filminspection device 1B according to the present embodiment. FIG. 5corresponds to (b) of FIG. 1. As illustrated in FIG. 5, the filminspection device 1B includes the same members as those included in thefilm inspection device 1, except for a concave reflecting roller 13A(first roller).

Unlike the reflecting roller 13, the concave reflecting roller 13A hassuch a shape that a diameter at a central part of the reflecting roller13A in a rotational axis direction of the reflecting roller 13Agradually decreases as compared with a diameter at both end parts of thereflecting roller 13A. A roller having this shape is often called“reverse crown roller.” The concave reflecting roller 13A thus has ashape by which the film 2 is stretched in the rotational axis directionof the concave reflecting roller 13A.

A depth of the concave reflecting roller 13A at the central part thereofis a value obtained by dividing, by two, a difference between thediameter at both end parts and the diameter at the central part. Anoptimum value of the depth in inspection of a defect of the film 2depends on a length of the concave reflecting roller 13A in therotational axis direction. For example, in a case where the length inthe rotational axis direction is 1000 mm, the depth is preferably notgreater than 1 mm. Note that an outer circumferential surface, facingthe film 2, of the concave reflecting roller 13A is constituted byunmated white vinyl chloride, in the same way as the reflecting roller13.

<<Operation and Advantageous Effect of Film Inspection Device 1B>>

The film 2 is carried while being in contact with an outercircumferential surface of the concave reflecting roller 13A at both endparts in the rotational axis direction. This causes the film 2 beingcarried to be stretched outward on the outer circumferential surface atthe both end parts, so that a crease or the like that is formed in thefilm 2 while the film 2 is being carried can be stretched. As a result,formation of a crease or the like in the film 2 is suppressed and,accordingly, a surface state of the film 2 can be more approximated touniformity. Therefore, with the film inspection device 1B, a change insurface state of the film 2 at a position where the film 2 is inspectedfor a defect is suppressed, so that a defect of the film 2 can beinspected more accurately.

Note that also in a case where the reflecting roller of the filminspection device 1B is a convex reflecting roller, formation of acrease or the like in the film 2 can be suppressed and, accordingly, thesurface state of the film 2 can be more approximated to uniformity. Theconvex reflecting roller is a reflecting roller whose diameter at acentral part of the reflecting roller in a rotational axis directionthereof gradually increases as compared with a diameter at both endparts of the reflecting roller. The present invention encompasses both(i) the above-described film inspection method carried out with use ofthe film inspection device 1B and (ii) the above-described filmproduction method carried out with use of the film inspection method.

(Replacement of Carrying Roller 3 a with Concave Roller Etc.)

The present invention also encompasses a film inspection device in whichthe carrying roller 3 a of the film inspection device 1 illustrated in(a) of FIG. 1 is replaced with a concave roller, a convex roller (crownroller), or an expander roller. That is, the carrying roller 3 a can bearranged such that the carrying roller 3 a is provided at a positionimmediately before the reflecting roller 13 along the carrying path ofthe film 2 and has a shape or a mechanism by which the film 2 isstretched in the rotational axis direction of the carrying roller 3 a.With the film inspection device described above, a crease or the like inthe film 2 is reliably stretched by the carrying roller 3 a before thefilm 2 is carried to the reflecting roller 13. Therefore, with the filminspection device, a change in surface state of the film 2 at a positionwhere the film 2 is inspected for a defect is reliably suppressed, sothat a defect of the film 2 can be inspected more accurately.

Further, the present invention also encompasses a film inspection devicein which the carrying roller 3 a of the film inspection device 1B isreplaced with a concave roller, a convex roller, or an expander roller.With the film inspection device described above, a change in surfacestate of the film 2 at a position where the film 2 is inspected for adefect is even more reliably suppressed, so that a defect of the film 2can be inspected more accurately.

Note, however, that in a case where the carrying roller 3 a has asufficiently well-working function of stretching a crease in the film 2,it may be more preferable that the reflecting roller 13, which is ageneral reflecting roller (having an outer circumferential surface thatis a cylindrical surface), be used instead of the concave reflectingroller 13A having a crease-stretching function. This is for thefollowing reason. That is, in a case where the concave reflecting roller13A is used, a crease in the film 2 may be stretched in the inspectionregion due to a crease-stretching function of the concave reflectingroller 13A, then a defect of the film 2 in the inspection region may beshifted, if slightly, in accordance with the stretching, andconsequently an error may be included in a position and size of thedefect measured by the inspection section 14. In a case where thegeneral reflecting roller 13 is used, on the other hand, such an erroris less likely to occur.

Modified Example 1

FIG. 6 is a lateral view illustrating a modified example of the filminspection device 1 illustrated in FIG. 1. (a) of FIG. 1 illustrates afilm inspection device 1C in which the carrying roller 3 b is providedon a Z-axis positive direction side with respect to the film 2, and (b)of FIG. 1 illustrates a film inspection device 1D in which the carryingroller 3 a is provided on the Z-axis positive direction side withrespect to the film 2. The present invention also encompasses the filminspection devices 1C and 1D in each of which one of the carryingrollers 3 a and 3 b is provided on a reflecting roller 13 side withrespect to the film 2 and the other of the carrying rollers 3 a and 3 bis provided on a side opposite to the reflecting roller 13 with respectto the film 2, as illustrated in (a) and (b) of FIG. 6. Each of the filminspection devices 1C and 1D provides advantageous effects in which theadvantageous effects brought about by the film inspection device 1 andthe advantageous effects brought about by the film inspection device 1Acoexist.

Modified Example 2 Film Inspection Device Including a Plurality ofLight-Receiving Devices

FIG. 7 is a cross-sectional view illustrating another modified exampleof the film inspection device 1 illustrated in FIG. 1. (a) of FIG. 7illustrates an arrangement in which a plurality of light-receivingdevices 12 are arranged in the X-axis direction, (b) of FIG. 7illustrates an arrangement in which a pair of light-receiving devices12A and 12B, which inspect respective inspection light that differ inwavelength, are arranged in the X-axis direction, and (c) of FIG. 7illustrates an arrangement in which a plurality of pairs of thelight-receiving devices 12A and 12B illustrated in (b) of FIG. 7 arearranged in the X-axis direction. Note that FIG. 7 corresponds to (b) ofFIG. 1. Also note that for the sake of simplicity, the light sources 11a and 11 b, the inspection section 14, and the carrying rollers 3 a and3 b are omitted in FIG. 7.

As illustrated in (a) of FIG. 7, a film inspection device 1E includesthe plurality of light-receiving devices 12. The film inspection device1E has the same arrangement as that of the film inspection device 1,except that the number of light-receiving devices 12 is differentbetween the film inspection device 1E and the film inspection device 1.Each of the plurality of light-receiving devices 12 collects inspectionlight from a part of the film 2 in the X-axis direction. The pluralityof light-receiving devices 12 as a whole collect inspection light fromalmost an entire region of the film 2 in the X-axis direction, by beingarranged in the X-axis direction. Note that the inspection section 14 isconnected to each of the plurality of light-receiving devices 12 (notshown).

The arrangement above allows reducing an area of the film 2 from whicharea each of the plurality of light-receiving devices 12 collectsinspection light. This enables, for example, a reduction in diameter ofthe lens of each of the plurality of light-receiving devices 12. Thissuppresses deformation of the field of view of the lens and coloraberration of the lens. Therefore, the film inspection device 1E caninspect a defect of the film 2 more clearly than the film inspectiondevices 1 and 1A through 1D, each of which has only a singlelight-receiving device 12.

As illustrated in (b) of FIG. 7, a film inspection device 1F includesthe pair of light-receiving devices 12A and 12B. The film inspectiondevice 1F has the same arrangement as that of the film inspection device1 except for the light-receiving device 12. Each of the light-receivingdevices 12A and 12B includes a lens which collects inspection light, andcollects inspection light from almost an entire region of the film 2 inthe X-axis direction.

In contrast to the light-receiving device 12 which includes two CCDs andtwo optical filters corresponding to the two CCDs, each of thelight-receiving devices 12A and 12B includes a pair made up of a CCD andan optical filter. The optical filter of the light-receiving device 12Atransmits only inspection light from the light source 11 a. As such, thelight-receiving device 12A can detect only inspection light from thelight source 11 a. The optical filter of the light-receiving device 12Btransmits only inspection light from the light source 11 b. As such, thelight-receiving device 12B can detect only inspection light from thelight source 11 b. Thus, wavelengths of inspection light respectivelyreceived by the light-receiving devices 12A and 12B are different fromeach other. Note that the inspection section 14 is connected to each ofthe light-receiving devices 12A and 12B (not shown).

As illustrated in (c) of FIG. 7, a film inspection device 1G includes aplurality of pairs of light-receiving devices 12A and 12B, each of thepairs being made up of the light-receiving device 12A and thelight-receiving device 12B illustrated in (b) of FIG. 7. The filminspection device 1G has the same arrangement as that of the filminspection device 1, except for the light-receiving device 12. Each pairof light-receiving devices 12A and 12B collects inspection light from apart of the film 2 in the X-axis direction. The plurality of pairslight-receiving devices 12A and 12B as a whole collect inspection lightfrom almost an entire region of the film 2, by being arranged in theX-axis direction. Note that the inspection section 14 is connected toeach of the light-receiving devices 12A and 12B (not shown).

With the arrangement above, the film inspection device 1G can inspect adefect of the film 2 more clearly than the film inspection devices 1 and1A through 1D, each of which has only a single light-receiving device12.

(Other Light-Receiving Devices)

The light-receiving device 12 can be a light-receiving device whichincludes (i) a photoreceiver including a lens and (ii) a spectrometerfor dispersing inspection light collected by the photoreceiver. In thisarrangement, the spectrometer disperses inspection light into spectra soas to divide the inspection light into a component of light from thelight source 11 a and a component of light from the light source 11 b,and converts each of the components into an electrical signal.

Further, the light-receiving device 12 can be a contact image sensor(CIS) module. The CIS module includes a plurality of image pickupdevices (e.g., CCDs) arranged in a single direction, optical filters,and a lens array. The optical filters are provided so as to correspondto the respective plurality of image pickup devices, and each of theoptical filters transmits only specific light so that a specific imagepickup device can convert only specific light into an electrical signal.The lens array is constituted by small lenses which are arranged in thesingle direction above. The arrangement above allows the CIS module to(i) split collected inspection light into a component of light from thelight source 11 a and a component of light from the light source 11 band (ii) convert each of the components into an electrical signal.

CONCLUSION

A film inspection device according to the present invention is a filminspection device including: a light-receiving device generating asignal by receiving light which returns via a film after having beenapplied to the film, the signal being for detecting a defect included inthe film; and a first roller carrying the film while supporting the filmfrom a side opposite to the light-receiving device in a field of view ofthe light-receiving device.

According to the arrangement above, the light-receiving device receiveslight which returns via the film after having been applied to the film.The film is carried while being supported by the first roller from theside opposite to the light-receiving device in the field of view of thelight-receiving device.

Accordingly, light received by the light-receiving device includes lightwhich returns via a part of the film which part is supported by thefirst roller, that is, via a part at which changes in position andposture of the film with respect to the light-receiving device aresuppressed. Consequently, according to the arrangement above, a changeunrelated to a defect of the film is less likely to occur in lightintensity of light received by the light-receiving device, as comparedwith an arrangement in which the first roller is not provided. As such,according to the film inspection device, the light-receiving device canoutput a signal which reflects a defect of the film more accurately ascompared with a conventional film inspection device that does notinclude the first roller.

Therefore, the film inspection device above can inspect a defect of afilm more accurately as compared with a conventional technique.

Note that examples of the ‘light that returns from the film’ encompasses(i) light which returns by being reflected from a surface or an insideof the film, (ii) light which returns by being scattered from thesurface or the inside of the film, and (iii) light which, after havingbeen transmitted through the film and then reflected or scattered by thefirst roller, returns by being transmitted through the film again.

Further, the film inspection device according to the present inventionis preferably arranged such that the first roller supports a part of thefilm which part is passed by an optical axis of the light-receivingdevice.

According to the arrangement above, light received by thelight-receiving device includes an increased proportion of light thatreturns via the part of the film at which part changes in position andposture of the film with respect to the light-receiving device aresuppressed. Accordingly, a change unrelated to the defect of the film iseven less likely to occur in light intensity. This makes it possible toinspect the film while carrying the film at high speed.

Further, the film inspection device according to the present inventionis preferably arranged such that the first roller is provided at aposition facing the light-receiving device via the film.

According to the arrangement above, light received by thelight-receiving device includes an increased proportion of light thatreturns via the part of the film at which part changes in position andposture with respect to the light-receiving device are suppressed.Accordingly, a change unrelated to the defect of the film is still evenless likely to occur in light intensity.

Further, the film inspection device according to the present inventionis preferably arranged such that light received by the light-receivingdevice includes the light received by the light-receiving deviceincludes light which, after having been transmitted through the film andthen reflected or scattered by the first roller, returns by beingtransmitted through the film again.

According to the arrangement above, the first roller can function as areflecting roller. As such, by adjusting properties (color, surfaceroughness, etc.) of an outer circumferential surface, which comes incontact with the film, of the first roller, (i) a contrast between apart corresponding to a normal part of the film and a part correspondingto a defective part of the film can be enhanced in light received by thelight-receiving device and (ii) a noise component included in the lightcan be reduced. This allows the film inspection device to inspect adefect of the film more accurately.

Further, the film inspection device according to the present inventionis preferably arranged such that an outer circumferential surface, whichcomes in contact with the film, of the first roller has a lightness ofnot less than 7 but not more than 9.5 according to the Munsell colorsystem and a chroma of not less than 0.5 but not more than 3 accordingto the Munsell color system.

Further, the film inspection device according to the present inventionis preferably arranged such that an outer circumferential surface, whichcomes in contact with the film, of the first roller has a glossiness ofnot less than 10 relative to a glossiness of 100 which corresponds to areflectivity of 10%, according to specular gloss at 60° which is a typeof specular gloss measuring method under Japanese Industrial StandardJIS-Z8741.

A foreign matter contained in the film often has a dark color. With thearrangement above, the above-described contrast can be enhanced, so thatthe film inspection device can inspect a defect of the film moreaccurately.

Further, the film inspection device according to the present inventionis preferably arranged such that the film inspection device furtherincludes a second roller provided at a position immediately before orafter the first roller along a carrying path of the film and on a sameside as the first roller with respect to the film.

According to the arrangement above, the first roller and the secondroller are provided on the same side with respect to the film. Thisallows securing more space for the light-receiving device. Accordingly,there is more flexibility in providing the light-receiving device in thefilm inspection device.

Further, the film inspection device according to the present inventionis preferably arranged such that the film inspection device furtherincludes a second roller provided at a position immediately before orafter the first roller along a carrying path of the film and on a sideopposite to the first roller with respect to the film.

According to the arrangement above, the second roller works so as topress the film against the first roller. This allows further suppressionof changes in position and posture of the film with respect to thelight-receiving device. Accordingly, the film inspection device caninspect a defect of the film more accurately.

Further, the film inspection device according to the present inventionis preferably arranged such that the second roller is provided at theposition immediately before the first roller along the carrying path ofthe film, and the second roller has a shape or a mechanism by which thefilm is stretched in a rotational axis direction of the second roller.

According to the arrangement above, a crease or the like in the film isreliably stretched by the second roller before the film is carried tothe first roller. Therefore, with the film inspection device, a changein surface state of the film at a position where the film is inspectedfor a defect is reliably suppressed, so that a defect of the film can beinspected more accurately.

Further, the film inspection device according to the present inventionis preferably arranged such that the first roller has a shape by whichthe film is stretched in a rotational axis direction of the firstroller.

The arrangement above allows the first roller to stretch a crease or thelike which is formed in the film while the film is being carried. As aresult, formation of a crease or the like in the film is suppressed and,accordingly, a surface state of the film can be more approximated touniformity. Therefore, with the film inspection device, a change insurface state of the film at a position where the film is inspected fora defect is suppressed, so that a defect of the film can be inspectedmore accurately.

A film inspection method according to the present invention is a filminspection method including the steps of: (a) generating a signal byreceiving light which returns via a film after having been applied tothe film, the signal being for detecting a defect included in the film;and (b) carrying the film while supporting the film from a side oppositeto the light-receiving device in a field of view of the light-receivingdevice.

The film inspection method above makes it possible to inspect a defectof a film more accurately as compared with a conventional technique.

A film production method according to the present invention is a filmproduction method including each step included in the film inspectionmethod above; and the step of (c) removing a defective portion of thefilm inspected on the basis of the signal generated in the step (a).

The film production method above makes it possible to produce a filmhaving fewer defects as compared with a conventional technique.

[Additional Matter]

The present invention is not limited to the embodiments, but can bealtered by a skilled person in the art within the scope of the claims.An embodiment derived from a proper combination of technical means eachdisclosed in a different embodiment is also encompassed in the technicalscope of the present invention.

REFERENCE SIGNS LIST

-   1 and 1A through 1G film inspection device-   2 film-   3 a and 3 b carrying roller (second roller)-   11 a and 11 b light source-   12, 12A, and 12B light-receiving device-   13 reflecting roller (first roller)-   13A concave reflecting roller (first roller)-   14 inspection section

The invention claimed is:
 1. A film inspection device comprising: alight-receiving device receiving inspection light which returns via afilm after having been applied to the film; a first roller carrying thefilm while supporting the film from a side opposite to thelight-receiving device in a field of view of the light-receiving device;a first light source applying visible light to the film; a second lightsource applying ultraviolet light or infrared light to the film; and aninspection section, the light-receiving device receiving, as theinspection light which returns via the film, the visible light and theultraviolet light or the infrared light, and the inspection sectionspecifying a type of the defect by comparing (a) a degree of change infirst intensity, which is an intensity of inspection light correspondingto the visible light which has been received by the light receivingdevice and (b) a degree of change in second intensity, which is anintensity of inspection light corresponding to the ultraviolet light orthe infrared light which has been received by the light-receivingdevice, the light-receiving device generating, based on the inspectionlight, an electrical signal for detecting a defect included in the film,the light-receiving device including (i) a lens which collects theinspection light, and (ii) a charge coupled device which converts theinspection light collected by the lens into the electrical signal, thefield of view of the light-receiving device being an area from which thelens can collect the inspection light to the charge coupled device, andin order to stretch the film in a rotational axis direction of the firstroller, the first roller having such a shape that a diameter at acentral part of the first roller in the rotational axis direction of thefirst roller gradually decreases or gradually increases as compared witha diameter at both end parts of the first roller.
 2. The film inspectiondevice as set forth in claim 1, wherein the first roller supports a partof the film which part is passed by an optical axis of thelight-receiving device.
 3. The film inspection device as set forth inclaim 1, wherein the first roller is provided at a position facing thelight-receiving device via the film.
 4. The film inspection device asset forth in claim 1, wherein the inspection light received by thelight-receiving device includes light which, after having beentransmitted through the film and then reflected or scattered by thefirst roller, returns by being transmitted through the film again. 5.The film inspection device as set forth in claim 1, wherein an outercircumferential surface, which comes in contact with the film, of thefirst roller has a lightness of not less than 7 but not more than 9.5according to the Munsell color system and a chroma of not less than 0.5but not more than 3 according to the Munsell color system.
 6. The filminspection device as set forth in claim 1, wherein an outercircumferential surface, which comes in contact with the film, of thefirst roller has a glossiness of not less than 10 relative to aglossiness of 100 which corresponds to a reflectivity of 10%, accordingto specular gloss at 60° which is a type of specular gloss measuringmethod under Japanese Industrial Standard JIS-Z8741.
 7. A filminspection device as set forth in claim 1, further comprising: a secondroller provided at a position immediately before or after the firstroller along a carrying path of the film and on a same side as the firstroller with respect to the film.
 8. The film inspection device as setforth in claim 7, wherein: the second roller is provided at the positionimmediately before the first roller along the carrying path of the film;and the second roller has a shape or a mechanism by which the film isstretched in a rotational axis direction of the second roller.
 9. A filminspection device as set forth in claim 1, further comprising: a secondroller provided at a position immediately before or after the firstroller along a carrying path of the film and on a side opposite to thefirst roller with respect to the film.
 10. The film inspection device asset forth in claim 1, wherein the first roller has a shape by which thefilm is stretched in a rotational axis direction of the first roller.11. The film inspection device as set forth in claim 1, wherein the filmis a film coated with a solution containing aramid, or a laminated filmon one side or both sides of which an aramid heat resistant layer isformed.
 12. A film inspection method, comprising the steps of: (a)applying a visible light to a film; (b) applying ultraviolet light orinfrared light to the film; (c) receiving, by a light-receiving device,the visible light and the ultraviolet light or the infrared light asinspection light which returns via the film after having been applied tothe film, the light-receiving device including (i) a lens which collectsthe inspection light, and (ii) a charge coupled device which convertsthe inspection light collected by the lens into an electrical signal;(d) generating, by the light-receiving device, the electrical signal fordetecting a defect included in the film; (e) carrying, by a firstroller, the film while supporting the film from a side opposite to thelight-receiving device in a field of view of the light-receiving device,the field of view of the light-receiving device being an area from whichthe lens can collect the inspection light to the charge coupled device,the first roller having such a shape that a diameter at a central partof the first roller in a rotational axis direction of the first rollergradually decreases or gradually increases as compared with a diameterat both end parts of the first roller; and (f) specifying a type ofdefect by comparing (i) a degree of change in first intensity, which isan intensity of inspection light corresponding to the visible lightwhich has been received by the light-receiving device and (ii) a degreeof change in second intensity, which is an intensity of inspection lightcorresponding to the ultraviolet light or the infrared light which hasbeen received by the light-receiving device.
 13. A film productionmethod comprising: each step included in the film inspection methodrecited in claim 12; and the step of (g) removing a defective portion ofthe film inspected on the basis of the defect specified in step (f). 14.The film production method as set forth in claim 13, wherein the film isa film coated with a solution containing aramid, or a laminated film onone side or both sides of which an aramid heat resistant layer isformed.
 15. The film inspection method as set forth in claim 12, whereinthe film is a film coated with a solution containing aramid, or alaminated film on one side or both sides of which an aramid heatresistant layer is formed.